Dielectric materials for electrical energy storage

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Prospect of texture engineered ferroelectric ceramics

Texture engineering offers an approach for achieving enhanced properties in bulk ceramics by introducing crystallographic anisotropy. Recent developments on texture engineering have enabled the fabrication of highly aligned ferroelectric ceramics with single-crystal-like electromechanical properties. In this paper, we review the history and recent progress of texture-engineered ferroelectric ceramics. We expect that more explorations on template-related issues, including orientation mismatch, physical models of the textured grain growth, and micromorphology-property relationship, will advance the development of texture-engineered ferroelectric ceramics with further improved properties

Flexocatalysis of nanoscale titanium dioxide

Piezocatalysis emerges as a distinctive approach for producing free radicals to drive catalysis. However, the piezoelectric effect exclusively manifests in non-centrosymmetric materials, which largely constraints the use of materials with centrosymmetry. To address this challenge, the concept of flexocatalysis is explored to bypass the structural constraints of materials by harnessing strain-gradient-induced polarization, taking advantage of universality of flexoelectricity. As an exemplar of flexocatalysis, centrosymmetric rutile titanium dioxide (TiO2) nano particles are selected due to its high permittivity, non-toxicity, biocompatibility, and wide-ranging utility. The effectiveness of flexocatalysis in generating free radicals (·H, and ·OH) is validated through hydrogen generation (∼2380 μmolg−1h−1 in pure water) and Rhodamine B dye degradation. Additionally, the size effect on flexoelectricity is examined both experimentally and theoretically, revealing that materials at nanoscale exhibit greatly enhanced flexoelectricity that can rival the traditional piezoelectricity. This work endows TiO2 with novel capabilities and broadens material's selection in mechanochemistry applications

NaNbO3 modified BiScO3-BaTiO3 dielectrics for high-temperature energy storage applications

Among the lead-free compositions identified as potential capacitor materials, BiScO3-BaTiO3 (BS-BT) relaxor dielectrics exhibit good energy storage performance. In this research, 0.4BS-0.6BT is considered as the parent composition, with NaNbO3 (NN) addition intended to substitute the A and B site cations. The NN modified BS-BT ceramics exhibit excellent temperature stability in terms of their dielectric properties, with the room-temperature dielectric constant on the order of 500–1 000 and variation less than 10% up to 400 °C. In addition, NN has a high band-gap energy leading to increased breakdown strength and energy storage properties in modified compositions. The highest breakdown strength was achieved for 0.4BS-0.55BT-0.05NN, being on the order of 430 kV/cm, and a high energy density of 4.6 J/cm3 with high energy efficiency of 90% was simultaneously achieved. Of particular importance is that the variation of the energy density was below 5% due to the temperature-insensitive dielectric constant, while ∼90% energy efficiency was retained over the temperature range of 25–160 °C. The improved temperature stability with NN addition makes this composition promising for high temperature capacitor and dielectric energy storage applications

Synthesis and high-temperature energy storage performances of fluorinated polyimides

In light of the increasingly stringent requirements for the applications of light-weight flexible high-temperature-resistant dielectric materials in the fields of aerospace, electronics, and electric vehicles, the imperative lies in the development of dielectric materials with high discharged energy density, enduring temperature resistance and high reliability. This work introduced side-chain trifluoromethyl (-CF3) groups into high-temperature engineering polymer polyimides and conducted comprehensive studies on the breakdown and energy storage capabilities. The introduction of bulky -CF3 substituents reduces the intermolecular interactions, increases the free volume, and suppresses the high-temperature leakage conductance loss by decreasing the formation of intermolecular charge transfer complexes between polymer chains. As a result, the fluorinated polyimides (PFI) with lower dielectric constant exhibit enhanced breakdown strengths (730 MV m−1 at 25 °C; 630 MV m−1 at 150 °C), leading to a high discharged energy density of 3.6 J cm−3 (∼1.7 times of pristine polyimides), alongside a charge-discharge energy efficiency of ∼80% at 150 °C. These findings underscore the great potential of PFI for applications in the field of high-temperature energy storage

Bi(Mg_0.5Hf_0.5)O₃-modified SrTiO₃ lead-free ceramics for high-temperature energy storage capacitors

Lead-free (1 − x)SrTiO –xBi(Mg Hf )O (0.05 ≤ x ≤ 0.4) ceramics were prepared by high-temperature solid-state sintering method. The microstructure, dielectric properties, and energy storage performance were investigated. The diffused phase transition was observed in samples with x ≥ 0.1, showing typical relaxor characteristic. In particular, 0.8ST-0.2BMH composition exhibits stable dielectric permittivity with variation below 15% over temperature range of − 100 °C to 185 °C, superior to that of undoped SrTiO . The calculated Weibull characteristic breakdown strength is 480 kV/cm for 0.8ST-0.2BMH ceramic, and a large energy density of 4.1 J/cm with high energy efficiency of 92% is obtained at electric field of 470 kV/cm. Of particular significance is that the energy efficiency remains above 91% at elevated temperature of 180 °C. In addition, fast discharge time (~ 0.88 µs) with high-power density of 2.8 MW/cm is achieved in 0.8ST-0.2BMH ceramic. All the above results indicate that the 0.8ST-0.2BMH relaxor dielectric is a promising lead-free ceramic for high-temperature energy storage applications. 3 0.5 0.5 3 3 3

Enhanced energy density and electric cycling reliability via MnO2 modification in sodium niobate‐based relaxor dielectric capacitors

Sodium niobate (NaNbO )‐based dielectrics have received much attention for energy storage applications due to their low‐cost, lightweight, and nontoxic nature. The field‐induced metastable ferroelectric phase in NaNbO ‐based dielectrics, however, leads to a large hysteresis of the polarization–electric field (P–E) loops and hence deteriorate the energy storage performance. In this study, the hysteresis was successfully reduced by introducing Bi and Ti into A‐site and B‐site of NaNbO , respectively. MnO addition was added to further increase the ceramic density and enhance the cycling reliability. As a result, a high recoverable energy density of 4.3 J/cm and a high energy efficiency of 90% were simultaneously achieved in the ceramic capacitor at an applied electric field of 360 kV/cm. Of particular importance is that the ceramic capacitor exhibits a stable energy storage properties over a wide temperature range of −70 to 170 °C, with much improved electric cycling reliability up to 10 cycles. [Figure not available: see fulltext.] 3 3 3 2 3+ 4+ 3

Perspectives on textured perovskite ferroelectric ceramics

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Low temperature sintering lead-free dielectric xBiScO3-(1-x)BaTiO3 for energy storage applications

Fabrication of ceramic capacitors requires technological breakthroughs to address growing concerns regarding sustainability, cost, and increased power consumption in the manufacturing process. Low temperature sintered xBiScO3-(1-x)BaTiO3 (BS-BT) with x = 0.4 is found to possess excellent energy storage performance and temperature stability. The grain size decreases from 3.5 μm sintered at 1100°C to less than 0.5 μm sintered at 800°C, leading to much improved breakdown field and energy storage properties. Recoverable energy density of 4.7 J/cm3 with a high efficiency of 89% was obtained at an electric field of 390 kV/cm, showing an excellent temperature stability over temperature range of 25–200°C and fatigue endurance for more than 105 cycles. Of particular importance is that the ceramic tape cofired with silver electrode over temperature range of 800–850°C shows no reaction and diffusion of silver at the electrode/ceramic interface, while a recoverable energy density of 3.3 J/cm3 was achieved with satisfactory efficiency of 80% at an electric field of 340 kV/cm when sintered in reduced atmosphere, expanding the electrode selection to low-cost base metal, such as Cu and Ni. This work provides a good paradigm in ceramic capacitor fabrications that will help reduce overall cost and power consumption by utilizing low temperature sintered lead-free dielectrics with comparable or even superior energy storage properties over state-of-the-art dielectrics. (Figure presented.)

Lead-free ferroelectric materials: Prospective applications

Abstract: The year of 2021 is the 100th anniversary of the first publication of ferroelectric behaviour in Rochelle salt, focussing on its piezoelectric properties. Over the past many decades, people witnessed a great impact of ferroelectricity on our everyday life, where numerous ferroelectric materials have been designed and developed to enable the advancement of diverse applications. Now the driving forces for ferroelectric studies stem from regulations on environment, human health and sustainable society development. This leads to the resurgence of lead-free ferroelectric materials for the expectation of replacing the state-of-the-art lead-based counterparts. The next wave of explorations into ferroelectric materials maybe related to the Internet-of-Things, which requires millions of self-powered sensors and memories. This will promote research on ferroelectrics for sensing, energy harvesting and storage, communication and non-volatile memories, from centimetre scale to micro and nanoscale. This review gives a brief discussion from the materials viewpoint, on the challenges and current status of lead-free ferroelectrics based on prospective applications. Graphic Abstract: [Figure not available: see fulltext.